The present invention relates to means of sealing off the inside of a pulverizer, especially a bowl-mill pulverizer that has a horizontal rotating bowl-type grinding ring rigidly connected to a shaft, from the outside atmosphere, comprising a barrier-air chamber and ring seals in a ring-seal holder.
The ring-seal holder in known bowl-mill pulverizers is connected to the pulverizer housing, into which hot gases are blown during pulverization to dry and convey the pulverized material (Aufbereitungs-Technik 12, 9, 543 [1971]). The housing is accordingly subjected to thermal stress. This stress is transferred to the ring-seal holder in the form of radial and axial expansion in relation to the grinding-ring shaft, which is erected and secured precisely on the drive flange of the pulverizer drive mechanism. This expansion must be accepted by the ring seals that seal the mechanism off from the shaft. The ring seals of known pulverizers are made of brass and rigidly secured in the ring-seal holder. The aforementioned expansion subjects them to increased wear, which can lead to leakage. The ring-seal holder is sealed off from the housing with a deformable ceramic cord. Ceramic cords can be compressed under unfavorable conditions to the extent that the seal will leak. The air blown into the barrier-air chamber penetrates into the pulverizer through a gap between the shaft and the ring-seal holder and, in conjuction with the aforesaid ring seals, seals off the inside of the pulverizer from the atmosphere.